.\" Copyright (c) 2018-2024 Yubico AB. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions are
.\" met:
.\"
.\"    1. Redistributions of source code must retain the above copyright
.\"       notice, this list of conditions and the following disclaimer.
.\"    2. Redistributions in binary form must reproduce the above copyright
.\"       notice, this list of conditions and the following disclaimer in
.\"       the documentation and/or other materials provided with the
.\"       distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
.\" HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
.\" OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd $Mdocdate: May 23 2018 $
.Dt FIDO_CRED_NEW 3
.Os
.Sh NAME
.Nm fido_cred_new ,
.Nm fido_cred_free ,
.Nm fido_cred_pin_minlen ,
.Nm fido_cred_prot ,
.Nm fido_cred_fmt ,
.Nm fido_cred_rp_id ,
.Nm fido_cred_rp_name ,
.Nm fido_cred_user_name ,
.Nm fido_cred_display_name ,
.Nm fido_cred_authdata_ptr ,
.Nm fido_cred_authdata_raw_ptr ,
.Nm fido_cred_clientdata_hash_ptr ,
.Nm fido_cred_id_ptr ,
.Nm fido_cred_aaguid_ptr ,
.Nm fido_cred_largeblob_key_ptr ,
.Nm fido_cred_pubkey_ptr ,
.Nm fido_cred_sig_ptr ,
.Nm fido_cred_user_id_ptr ,
.Nm fido_cred_x5c_list_count ,
.Nm fido_cred_x5c_list_ptr ,
.Nm fido_cred_x5c_ptr ,
.Nm fido_cred_attstmt_ptr ,
.Nm fido_cred_authdata_len ,
.Nm fido_cred_authdata_raw_len ,
.Nm fido_cred_clientdata_hash_len ,
.Nm fido_cred_id_len ,
.Nm fido_cred_aaguid_len ,
.Nm fido_cred_largeblob_key_len ,
.Nm fido_cred_pubkey_len ,
.Nm fido_cred_sig_len ,
.Nm fido_cred_user_id_len ,
.Nm fido_cred_x5c_list_len ,
.Nm fido_cred_x5c_len ,
.Nm fido_cred_attstmt_len ,
.Nm fido_cred_type ,
.Nm fido_cred_flags ,
.Nm fido_cred_sigcount
.Nd FIDO2 credential API
.Sh SYNOPSIS
.In fido.h
.Ft fido_cred_t *
.Fn fido_cred_new "void"
.Ft void
.Fn fido_cred_free "fido_cred_t **cred_p"
.Ft size_t
.Fn fido_cred_pin_minlen "const fido_cred_t *cred"
.Ft int
.Fn fido_cred_prot "const fido_cred_t *cred"
.Ft const char *
.Fn fido_cred_fmt "const fido_cred_t *cred"
.Ft const char *
.Fn fido_cred_rp_id "const fido_cred_t *cred"
.Ft const char *
.Fn fido_cred_rp_name "const fido_cred_t *cred"
.Ft const char *
.Fn fido_cred_user_name "const fido_cred_t *cred"
.Ft const char *
.Fn fido_cred_display_name "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_authdata_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_authdata_raw_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_clientdata_hash_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_id_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_aaguid_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_largeblob_key_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_pubkey_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_sig_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_user_id_ptr "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_x5c_list_count "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_x5c_list_ptr "const fido_cred_t *cred" "size_t idx"
.Ft const unsigned char *
.Fn fido_cred_x5c_ptr "const fido_cred_t *cred"
.Ft const unsigned char *
.Fn fido_cred_attstmt_ptr "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_authdata_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_authdata_raw_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_clientdata_hash_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_id_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_aaguid_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_largeblob_key_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_pubkey_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_sig_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_user_id_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_x5c_list_len "const fido_cred_t *cred" "size_t idx"
.Ft size_t
.Fn fido_cred_x5c_len "const fido_cred_t *cred"
.Ft size_t
.Fn fido_cred_attstmt_len "const fido_cred_t *cred"
.Ft int
.Fn fido_cred_type "const fido_cred_t *cred"
.Ft uint8_t
.Fn fido_cred_flags "const fido_cred_t *cred"
.Ft uint32_t
.Fn fido_cred_sigcount "const fido_cred_t *cred"
.Sh DESCRIPTION
FIDO2 credentials are abstracted in
.Em libfido2
by the
.Vt fido_cred_t
type.
The functions described in this page allow a
.Vt fido_cred_t
type to be allocated, deallocated, and inspected.
For other operations on
.Vt fido_cred_t ,
please refer to
.Xr fido_cred_set_authdata 3 ,
.Xr fido_cred_exclude 3 ,
.Xr fido_cred_verify 3 ,
and
.Xr fido_dev_make_cred 3 .
.Pp
The
.Fn fido_cred_new
function returns a pointer to a newly allocated, empty
.Vt fido_cred_t
type.
If memory cannot be allocated, NULL is returned.
.Pp
The
.Fn fido_cred_free
function releases the memory backing
.Fa *cred_p ,
where
.Fa *cred_p
must have been previously allocated by
.Fn fido_cred_new .
On return,
.Fa *cred_p
is set to NULL.
Either
.Fa cred_p
or
.Fa *cred_p
may be NULL, in which case
.Fn fido_cred_free
is a NOP.
.Pp
If the CTAP 2.1
.Dv FIDO_EXT_MINPINLEN
extension is enabled on
.Fa cred ,
then the
.Fn fido_cred_pin_minlen
function returns the minimum PIN length of
.Fa cred .
Otherwise,
.Fn fido_cred_pin_minlen
returns zero.
See
.Xr fido_cred_set_pin_minlen 3
on how to enable this extension.
.Pp
If the CTAP 2.1
.Dv FIDO_EXT_CRED_PROTECT
extension is enabled on
.Fa cred ,
then the
.Fn fido_cred_prot
function returns the protection of
.Fa cred .
Otherwise,
.Fn fido_cred_prot
returns zero.
See
.Xr fido_cred_set_prot 3
for the protection policies understood by
.Em libfido2 .
.Pp
The
.Fn fido_cred_fmt
function returns a pointer to a NUL-terminated string containing
the attestation statement format identifier of
.Fa cred ,
or NULL if
.Fa cred
does not have a format set.
.Pp
The
.Fn fido_cred_rp_id ,
.Fn fido_cred_rp_name ,
.Fn fido_cred_user_name ,
and
.Fn fido_cred_display_name
functions return pointers to NUL-terminated strings holding the
relying party ID, relying party name, user name, and user display
name attributes of
.Fa cred ,
or NULL if the respective entry is not set.
.Pp
The
.Fn fido_cred_authdata_ptr ,
.Fn fido_cred_authdata_raw_ptr ,
.Fn fido_cred_clientdata_hash_ptr ,
.Fn fido_cred_id_ptr ,
.Fn fido_cred_aaguid_ptr ,
.Fn fido_cred_largeblob_key_ptr ,
.Fn fido_cred_pubkey_ptr ,
.Fn fido_cred_sig_ptr ,
.Fn fido_cred_user_id_ptr ,
.Fn fido_cred_x5c_ptr ,
and
.Fn fido_cred_attstmt_ptr
functions return pointers to the CBOR-encoded and raw authenticator
data, client data hash, ID, authenticator attestation GUID,
.Dq largeBlobKey ,
public key, signature, user ID, x509 leaf certificate, and attestation
statement parts of
.Fa cred ,
or NULL if the respective entry is not set.
.Pp
The corresponding length can be obtained by
.Fn fido_cred_authdata_len ,
.Fn fido_cred_authdata_raw_len ,
.Fn fido_cred_clientdata_hash_len ,
.Fn fido_cred_id_len ,
.Fn fido_cred_aaguid_len ,
.Fn fido_cred_largeblob_key_len ,
.Fn fido_cred_pubkey_len ,
.Fn fido_cred_sig_len ,
.Fn fido_cred_user_id_len ,
.Fn fido_cred_x5c_len ,
and
.Fn fido_cred_attstmt_len .
.Pp
The
.Fn fido_cred_x5c_list_count
function returns the length of the x509 certificate chain in
.Fa cred
and the
.Fn fido_cred_x5c_list_ptr
and
.Fn fido_cred_x5c_list_len
functions return a pointer to and length of the x509 certificate at index
.Fa idx
respectively.
Please note that the leaf certificate has an
.Fa idx
(index) value of 0 and calling
.Fn fido_cred_x5c_list_ptr cred 0
and
.Fn fido_cred_x5c_list_len cred 0
is equivalent to
.Fn fido_cred_x5c_ptr cred
and
.Fn fido_cred_x5c_len cred
respectively.
If
.Fa idx
exceeds the return value of
.Fn fido_cred_x5c_list_count ,
.Fn fido_cred_x5c_list_ptr
returns NULL and
.Fn fido_cred_x5c_list_len
returns 0.
.Pp
The authenticator data, x509 certificate, and signature parts of a
credential are typically passed to a FIDO2 server for verification.
.Pp
The
.Fn fido_cred_type
function returns the COSE algorithm of
.Fa cred .
.Pp
The
.Fn fido_cred_flags
function returns the authenticator data flags of
.Fa cred .
.Pp
The
.Fn fido_cred_sigcount
function returns the authenticator data signature counter of
.Fa cred .
.Sh RETURN VALUES
The authenticator data returned by
.Fn fido_cred_authdata_ptr
is a CBOR-encoded byte string, as obtained from the authenticator.
To obtain the decoded byte string, use
.Fn fido_cred_authdata_raw_ptr .
.Pp
If not NULL, pointers returned by
.Fn fido_cred_fmt ,
.Fn fido_cred_authdata_ptr ,
.Fn fido_cred_clientdata_hash_ptr ,
.Fn fido_cred_id_ptr ,
.Fn fido_cred_aaguid_ptr ,
.Fn fido_cred_largeblob_key_ptr ,
.Fn fido_cred_pubkey_ptr ,
.Fn fido_cred_sig_ptr ,
and
.Fn fido_cred_x5c_ptr
are guaranteed to exist until any API function that takes
.Fa cred
without the
.Em const
qualifier is invoked.
.Sh SEE ALSO
.Xr fido_cred_exclude 3 ,
.Xr fido_cred_set_authdata 3 ,
.Xr fido_cred_set_pin_minlen 3 ,
.Xr fido_cred_set_prot 3 ,
.Xr fido_cred_verify 3 ,
.Xr fido_credman_metadata_new 3 ,
.Xr fido_dev_largeblob_get 3 ,
.Xr fido_dev_make_cred 3
